Heretofore, cutting tools, etc. are prepared by coating the surface of a ceramic substrate with a diamond film. However, such a diamond film is so insufficient in adhesion as their tips cause chipping.
More description will be made on this point. For instance, Japanese Patent Publication (kokoku) No. 59,086/1985, and Japanese Patent Laid-open (kokai) Publication Nos. 109,628/1986 and 291,493/1986 disclose technology which involves using a silicon nitride substrate or a ceramic substrate having a particular thermal expansion coefficient in order to provide a diamond-coated material having high adhesion.
These technology, however, each involves prevention of the diamond film from peeling off by suppressing the thermal stress generating upon cooling after the formation of the diamond film, yet its adhesion is not yet sufficient.
For instance, when chips with such a diamond film coated thereon are used for cutting, their tips may still cause chipping.
The object of the present invention is to provide a diamond-coated body which has so high in adhesion of its diamond film as to avoid chipping and which can be prepared with ease.